In the provision of industrial systems for bottling liquids or for packaging goods of various kinds, the design of suitable systems for moving the products from one processing station to the next and toward the store is very important.
In performing the production cycles provided by these systems, it is often necessary to convey and stop the conveyed products in chosen positions, so as to be able to perform the various steps provided by such process, such as for example the filling of bottles, their closure, or the packaging of products of various kinds, or the accumulation of packages or containers.
Known types of conveyor chain, composed of a plurality of links which are mutually interconnected so as to form a chosen path, which can comprise straight and curved portions, are currently in use for moving goods within systems in which the working cycles provide for conveying or stopping the products in one or more positions.
One particularly strongly felt need is to allow the products to stop in the chosen positions without requiring the simultaneous stopping of the conveyor chain, which would entail high complexity in production and high costs for its operation.
For this purpose, it is known to manufacture conveyor chains which are constituted by interconnecting a plurality of links, each of which comprises a base body which has a substantially rectangular plan shape and on the transverse sides of which one or more shafts are supported which are arranged longitudinally with respect to the base body and transversely to the direction of advancement of the products on the chain; a plurality of rollers are associated with said shafts so that they can rotate freely and constitute the upper conveyance surface of the chain. A first known type of link provides, on the transverse sides of the base body, a plurality of seats which are approximately U-shaped and are open upward for supporting the one or more shafts, the ends of which are inserted from above into said seats; a plurality of mutually identical rollers are associated rotatably on said shafts.
A second known type of link has, at the transverse sides of its base body, a plurality of through holes, which are for example aligned in pairs and within which the ends of the one or more shafts are inserted and thus supported; a plurality of mutually identical rollers are associated rotatably with these shafts as well.
In both of these known embodiments, if the products to be moved have bulky loads, the shafts, owing to their longitudinal extension, are made to rest, in one or more of their intermediate points, on a corresponding number of supports, which protrude upward from the base body and have a seat for rotatably accommodating a portion of said shaft.
The presence of the rollers in said links of the known type allows to convey the products and to stop them without having to interrupt the movement of the conveyor chain.
The moved product can in fact be blocked in the chosen position by means of a retention barrier without generating an intense friction force with respect to said chain thanks to the interposition of the rollers which, by rotating about the shaft that supports them, reduce drastically the extent of said force; in this manner, the presence of stationary objects on the chain does not constitute a hindrance to the advancement of said chain.
The main drawback that can be observed in these known types of conveyor chain is that they have high wear of the intermediate supports, since the shaft that rests on them, if turned by the rollers that it supports, slides continuously on said intermediate supports, even in the presence of light loads on the conveyor chain.
Another drawback of known types of conveyor chain is that since each shaft rests directly on the corresponding intermediate support, it is extremely difficult to clean this region of the conveyor chain, and therefore debris from the outside environment or from the conveyed products, such as for example dust or splinters caused by the breakage of glass bottles, can penetrate between the shaft and the intermediate supports, increasing the drag of the chain and accelerating its wear; accordingly, long line downtimes are necessary in order to perform the required cleaning operations.
Another drawback of said known types of conveyor chain is that at the intermediate supports there is a considerable discontinuity in the upper supporting surface, which may give rise to an imperfect placement of the product on the chain, especially when such product has a narrow resting base, consequently hindering the correct execution of the cycle of the system within which said chain is inserted.
Finally, the use of a large number of rollers entails a considerable cost increase, since usually each link has at least three rows of rollers and each chain can be tens of meters long.